Preheat your oven to 350°F (175°C).

In a large bowl, combine ground beef, breadcrumbs, egg, chopped onion, minced garlic, Worcestershire sauce, salt, pepper, and Italian seasoning. Mix until well combined.

Transfer the meat mixture to a loaf pan. Press it down evenly and compactly to form a solid loaf.

Place the loaf pan in the preheated oven and bake for 30-35 minutes, or until the internal temperature reaches 160°F (70°C).

While the meatloaf is baking, bring a large pot of salted water to a boil and cook elbow macaroni according to package instructions until al dente. Drain and set aside.

In a saucepan, melt 2 tablespoons of butter over medium heat. Stir in the flour and cook for 1-2 minutes until lightly golden.

Gradually whisk in milk, mustard powder, salt, and pepper. Continue to whisk until the sauce thickens. Remove from heat, and stir in the shredded cheddar cheese until melted.

In a large bowl, mix the cooked macaroni with the cheese sauce. Stir until the pasta is well-coated with the cheese mixture.

Once the meatloaf is done baking, increase oven temperature to 375°F (190°C).

Carefully remove the meatloaf from the loaf pan and slice it into thick pieces.

In a greased baking dish, layer half of the mac and cheese, followed by a layer of meatloaf slices, and then the remaining mac and cheese on top.

In a small bowl, combine 1/2 cup breadcrumbs, 1/2 cup shredded cheddar cheese, and melted butter. Sprinkle this mixture over the top of the assembled casserole.

Return the casserole to the oven and bake for an additional 20-25 minutes, or until the topping is golden brown and the cheese is bubbly.

Remove from the oven and let it cool for a few minutes before serving. Enjoy your Mac and Cheese Meatloaf Casserole warm!